It is well known for relatively simple cameras, such as recent one-time-use cameras, to include a manual film wind thumbwheel that is rotatable in engagement with a film spool to similarly rotate the spool to take-up a filmstrip. In most one-time-use cameras, the spool is part of a film cartridge and is rotatable inside the cartridge shell to take-up successive exposed frames of the filmstrip.
Typically, the thumbwheel includes a peripheral series of interdental spaces which are intended to be stroked by one's thumb to grip the peripheral edge of the thumbwheel and windingly rotate the thumbwheel. In some one-time-use cameras, the interdental spaces are located partially inside and partially outside the camera housing.
If a film metering pawl inside the camera was to be located to pivot into one of the interdental spaces to arrest the thumbwheel each time a fresh frame of the filmstrip is positioned for exposure, the interdental spaces would need to be made fairly shallow and narrow to accommodate the relatively small pawl. The film metering pawl would be moved out of the interdental space after the film frame is exposed, to permit the thumbwheel to be rotated to rotate the spool to take-up the exposed frame, However, it would be difficult for one's thumb to grip the peripheral edge of the thumbwheel and windingly rotate the thumbwheel when the interdental spaces are made fairly shallow and narrow.
If an anti-backup pawl inside the camera housing was to be urged into successive ones of the interdental spaces to prevent counter-rotation of the thumbwheel, the interdental spaces would need to be made fairly shallow and narrow to accommodate the relatively small pawl. Thus, the same problem as in the example of the film metering pawl will occur.